Yet another Denford for the collection (Triac Retrofit thread)

[Tom J]

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Now as I mentioned earlier about theory and real world, using a reasonably accurate multimeter, I get around 52VDC at the capacitor. That's a good 14% higher than our calculated figure. This will drop under load, but it may also rise above that under hard deceleration of motors, which is why you should always allow a reasonable safety margin between your power supply voltage and the maximum allowable stepper driver voltage.

Your driver EM806 has operating voltage up to +80 VDC so why 52VDC satisfy you?

[m_c]

Your driver EM806 has operating voltage up to +80 VDC so why 52VDC satisfy you?

Because theoretically the x and y motors are only good for 57V, and running them higher could result in overheating them.
Off course you could avoid motor overheating by reducing current, but then you reduce torque at all speeds, which is counter productive to getting the best performance.